Mix with hot water to make hot chocolate.
A Brookfield Powder Flow Tester, equipped with Powder Flow Pro software for automated instrument control and data acquisition, was used to test a name brand (Brand X) and a generic (Brand Y) hot chocolate mix. The hot chocolate mixes were scooped into the trough, and the scraping tool was then used to evenly distribute the powder throughout the trough. After recording the sample weights and entering it into the software, a standard flow function test and then a wall friction test were run. Time required for each test was 35 minutes and 20 minutes respectively.
Figure 1: Hot Chocolate Mix Flow Function Graph
Figure 1 shows the flowability of the hot chocolate mixes at different levels of consolidating stress. These results show that the hot chocolate mixes have very similar flow characteristics. Both mixes are generally easy flowing except at very low levels of consolidating stress where it begins to fall into the cohesive range (below .5 kPa).
Figure 2: Hot Chocolate Mix Wall Friction Graph
Figure 2 represents the angles of wall friction at different levels of normal stress. Angles of wall friction represent the friction between the sliding powder and the wall of the hopper or chute at the onset of flow. In this test a stainless steel lid was used, illustrating what the friction would be like if the hot chocolate mixes were in a stainless steel hopper. At a low normal stress of about .5 kPa, the effective angle of wall friction was about 28º for brand X and 25º for brand Y and goes down to about 20º and 19º, respectively, at higher levels of Normal Stress (kPa).
Figure 3: Hot Chocolate Mix Bulk Density Graph
Figure 3 shows the bulk density of the materials at different levels of consolidating stress. This graph tells us that the hot chocolate mixes have fill densities of 650 kg/m³ and 619 kg/m³ and rise to about 800 kg/m³ and 767 kg/m³ at around 10 kPa of consolidating stress. In general, a free flowing powder will show very small changes in bulk density, whilst a cohesive or poor flowing powder will generally show a large increase in bulk density.
The brand name hot chocolate mix and the generic hot chocolate mix have very similar flow characteristics. Both powders are generally easy flowing and should not experience too many flow problems. The critical arching dimensions, of°.964in (24.1mm) and 1.108in (27.7mm) provide a conservative estimate to prevent arching from happening, provided the minimum outlet dimension of the hopper exceeds this value. These values are significantly low, meaning arching should not be a real problem. The critical ratholing dimension is dependent on the diameter of the bin. Powder Flow Pro can automatically calculate the rathole diameter once the bin diameter is entered.